The sign of degrees (°) is used in this work to represent feet, and the sign of minutes (′) inches. The illustrations which accompany each species and important variety are one half the size of nature, except in the case of a few of the large Pine cones, the flowers of some of the Magnolias, and the leaves and flower-clusters of the Palms. These are represented as less than half the size of nature in order to make the illustrations of uniform size. These illustrations are from drawings by Mr. Faxon, in which he has shown his usual skill and experience as a botanical draftsman in bringing out the most important characters of each species, and in them will be found the chief value of this Manual. For aid in its preparation I am indebted to him and to my other associates, Mr. Alfred Rehder and Mr. George R. Shaw, who have helped me in compiling the most difficult of the keys. C. S. Sargent. Arnold Arboretum, Jamaica Plain, Mass. January, 1905. TABLE OF CONTENTS Map of North America (exclusive of Mexico) showing the eight regions into which the country is divided according to the prevailing character of the trees _Frontispiece_ Synopsis of the Families of Plants described in this work xi Analytical Key to the Genera of Plants described in this work, based chiefly on the character of their leaves xvi Manual of Trees 1 Gymnospermæ 1 Angiospermæ 96 Monocotyledons 96 Dicotyledons 118 Apetalæ 118 Petalatæ 342 Polypetalæ 342 Gamopetalæ 790 Glossary of Technical Terms 893 Index 899 SYNOPSIS OF THE FAMILIES OF PLANTS DESCRIBED IN THIS BOOK Class I. GYMNOSPERMÆ. Resinous trees; stems formed of bark, wood, or pith, and increasing in diameter by the annual addition of a layer of wood inside the bark; flowers unisexual; stamens numerous; ovules and seeds 2 or many, borne on the face of a scale, not inclosed in an ovary; embryo with 2 or more cotyledons; leaves straight-veined, without stipules.